Telephone system



May 12, 1931. T. F. CROCKER TELEPHONE SYSTEM Original Filed April 28, 1928 HUT Patented May 12, 1931 UENITEE s it-ares ATENT mm V Y '"r'fioiims{rJ'cRocKER/or"CHICAGO, 'riinrn'ors, ess enon- TO easem nt -mm enn- "PANY, or Kansas-on y,ivnsscnnz, A 'oonronarrom or DELAWARE esrnenona srsrnivr application and aqnn ices-{seem N0. $273544. Renewed em-her is, 1920.

This invention pertains to telephone systems in igeneral hut is moreparticul arly concerned with operators cord circuitsandtru'nk circuits. 7

A telephone SWltChbQ'afdjnfiy terminate trunks from a numberofdifferent points at which signalling current of the same --fre-" quency-inay'or may not be used. To-avoid the neeessityo'f providing a ringing current responsive relay in the operators cords-adjusted to respond to-thedifierentfrequencies of ringing current 'and adj uste'd to operate over all the trunks, which may vary Widely in charaeteristics a separate ringing current responsiverelay-maybe provided for each of the trunks 't-erminatimg the switchboard espeoially adj ustedt'ior the trun-k, with means controlled by the ringing current responsive relay of, the trunk to-r --controlling the ringdown signal 'in'th-e toll-operatofs cord. In practice 'it ha 's 'beeniound convenient to render-this control over the sleeve conductor of the-cord and trunk. Vhen trunks terminate at "a switchboard from :a number of difierent points it/is also aproh'ablethat signallingcurrent 'of difi'erent :frequencies will he required to signal 'over'thedifferent trunks to control the signals at the distant points. A convenient method of meeting this requirement is to provideeach trunk with means for app-lying ringing current of the particular trequency necessary for'thattrunk, which-means will respond'to the'o'peration'of single ring 7 ing key in theperators cord; I

Th e object of this --i-nvention' is the producion of i a new and improved trunk "circuit flior a two-way trunl'z which contains means for controlling the ring-down signal in the ppera'tors =c'ord circuit over the sleeve conducter, and also contains ineans for-applying'signailing current over the t unk conductors which means I responsive t'o the operation of the ringing key in the 'operators cord.

- The particular features of this invention 53 will be described in detail in the "following specifications with then-id of the acco'mpanyinjg di awing, in which is shown by means of the usual; schematic J circuit diagrams a prete rred embodiment of the invention.

the drawing, a section an "operato cord is shown at O terminating in {plug 1 and provided with the listening keyK and the ringing key K A trunk comprising conductors 4 and 5 is shown terminating at an answeringaposition in'the. jack J and having a multiple extending to an auxiliary position and terminating thereat in th e jack'J An understanding of the operation o f'the apparatus involved and the features of the invention may best be obtaine d from detailed descriptions of the operationsinvolved'in-the completing of connections. For thispur pose, it will first be assumed that -a-call has been extended from a distantipoint over the trunk line comprisingconductors 4 and 5. To signal the operator at 'the answering position shown, ringing current is momentarily applied to the trunk conductors atthe distant point causing the operationot ringing current responsive "relay 10. -Relay in operati-n-g,-removes the normal short-circuit fr'oin the signal-control relay-1 30. RelayBO there uponopjerates over the circuit including contacts 45, and at contacts 32 opens another point in-its normal short-circuit so thatthis relay remains operated after relay: 10 re: stores Relay in operating, also grounds control conductor at contact 31, thereby cl'osinga circuit for'the visual signals V1 and V2 by way of contacts 5-1 and 41. Visuals and V2 operate to mark the trunk busy. "The grounding of conductor 70 also closes thecircuit of lamp L l at the answering position. The lighting of lamp'Ll apprises the opera torof the incoming call. i 1

The operator answers the call by inserting the plug of an idle cord, such asplug P'of the cord 0, into jack J, and then actuating the listening key K. Inserting plug Pinto ack J closes contacts :2 which completes a circuit including contacts 53 for the upper winding of unlockingrelay 40. Relay eo operates"and closes anew circuit for visuals and V2 at contacts 42, opens the circuit o-fre1'ay30jhy separating contacts 45 and closes a circuit for sleeve relay 50 at contacts Kenyan restores, opening the circuit of lamp L by removing ground from conductor TO atconta'cts 31. The circuit closed forrelay '50'includes its two windings in series, enacts 62y$1 eve of jack J1 and plug P, contacts 4, contacts 3, and lamp L. The current flow in this circuit is insuflicient to cause lighting of lamp L. Relay operates, however, and opens the circuit of the upper winding of relay 40 by separating contacts 53. At contacts a circuit is prepared for later shunting the lower high resistance winding of relay 50 as will be described subsequently, and at contacts 52 a new circuit is prepared for visuals V1 and V2 which is closed as soon as relay 4O falls back and again closes contacts 41. Relay 40, in restoring also opens the initial energizing circuit of relay 50 at contacts 44, but relay 50, once operated, holds up in series with resistance R2. 7

After operating the listening key K, the operator may converse with the distance calling operator, and then complete the desired connection. Operatingkey K, by separating contacts 3, inserts resistance R in the sleeve circuit in place of lamp L. The resistance of R is considerably higher than the resistance of lamp L so that the current in the sleeve circuit is considerably reduced when key K is operated. Since relay 50 is being energized over its-two winding in series, however, it remains operated. After the connection is completed, the operator restores the key K to normal, again placing lamp L in the sleeve circuit.

At the termination of the call, the calling operator receives the usual disconnect signal and then gives the operator at the position shown the ring down signal by again projecting ringing current over the trunk conductors. Again relay 1O responds, causing the operation of relay 30. Relay 30, by grounding conductor at contacts 31, now shunts the lower winding of relay 50. This increases the current in the sleeve circuit sufiiciently to cause the lighting of lamp L, thereby signalling the operator. The operator will then either remove the plug P from jack J or opcrate key K to converse with the distance calling operator. Should she do the latter, resistance R is again inserted in the sleeve circuit.

' This again decreases the current in the sleeve circuit, and since relay 50 is now energized over its upper low resistance winding only,

a this relay falls back, again closing the circuit for relay 40 at contacts 53. Relay 40 operates and unlocks relay 30 by separating contacts 45, and again closes the circuit for relay 50 over its two windings in series at contacts 44.

Relay 50 thereupon rel-operates and remains jack J upon receiving the disconnect signal, the following operation takes place, remembering that relay 30 is operated at this time and that relay 50 is being held energized over its upper winding. As soon as the tip of the plug P disengages the tip spring of jack J, contacts 2 separate. The following circuit, including the lower winding of relay 40, contacts 54, contacts 52, contacts 41, and the two visual signals V1 and V2 in parallel, becomes eifective to cause relay 40 to energize. Relay 40, in energizing, again opens the circuit of relay 30 by separating contacts 45 to allow this relay to restore. Relay 50, of course, also falls back when the plug P is completely removed from jack J, opening the circuit including the two visual signals V1 and V2 in parallel and the lower winding of relay 40 at contacts 54. The trunk circuit of the trunk isthus restored to its normal condition. 7

To further describe the invention, it will be assumed that the operator at the answering position wishes to extend a connection to the distant point to which the trunk comprising conductors 4 and 5 extends, and chooses this trunk and the cord 0 to do so. To extend the connection, the toll operator inserts plug P into jack J and then momentarily operates ringing key K2. Inserting plug P into jack J; by closing contacts 2, closes a circuit for the upper winding of relay 40. Relay 40 energizes and closes a circuit for visuals V1 and V2 at contacts 42, and closes a circuit for relay 50 at contacts 44. Relay 50 operates as previously described and again causes relay 40 to fallback.

When the operator operates key K2, high resistance R is inserted in the sleeve circuit which sufiiciently limits the current in this circuit to cause relay 50 to again fall back. Relay 40 again operates over its upper winding over the circuit including contacts 53 and connects relay 20 and the lower talking conductor at contacts 43. Relay 20 now operates over the circuit including the lower talking conductor, ring of jack J and plug P to battery through the lower contacts on key K Relay 20, in operating, opens the normal ringing bridge including relay 10 across the tip and ring of jack J at contacts 21 and 25 and connects a source ringing current of the proper frequency to trunk conductors 4 and 5 at contacts 23 and 24.

When key is again restored, relay 50 is again operated and relay 40 is deenergized whereupon relay 20 is again disconnected from the lower talking conductor. Belay 20 then restores to normal. Further operations concerning the completing of the connections need not'be described.

, Another feature of this invention includes the manner in which a call answered by the operator at the answering position may be transferred to the auxillary position. To describe the mannerin which the transfer is accomplished it may loe assumed that an incoming call over {the trunk comprising conductors "4 and '5 have been-answeredby the operator at the answering position. To transfer the callfto thefau xiliary position, the operatorat the answering positi'onmm 'mentarily operates key-K. This 1 causes the lighting of lamp L2 at-the auxiliarypoSition to signal theoperator thereat ajnd also closes thecircuit of relay-60. Relay 60 operates and at contacts 62 opensthe circuit of relay 50, prepares [a locking circuit tor itself at contacts ,6-3, and preparesa circuit for relay 4O at;conta=cts"4ll As'soon-as-relay deenergi'zes, the circuit of the upper winding of relay 40 is closedjat contacts 53. Relay 40 energizes "and closes the locking circuit for relay. at contacts 42.

When the operator at the auxiliary' position inserts the plug of her "cord into jack glare-lay 50 operates over its two windings in {SQIlGS over the sleeve o'f jack J 2 and,-as previously "described, causes the d'eenergizationpi' relay 4'0. Relay 40, by opening contacts 46, opens'the'locliing circuit of relay 60, which ,relay thereupon restores to normal. It is to be noted that the condition of the trunk circuit is ,now thesanie as it was after theop-erator at the ans'werin'g'position answere d' the call. Further ope-rations are similar to those previously described.

This completes the description of the operation of this invention. 'W'ha t is considered new and is desired tohave protected by Letters Patent is specifically stated in the ap pended claims.

What is claimed is:

l 1. In a telephoneisys-tem, a trunk, a cord circuit and means for connecting it to said tr i 1nk,ja call signal for the trunk, a 'cord signal in {the cord, a double-Wound sleeve relay for controlling said call signal, means for energizing sai'dsleeve relay over both its windings and a non-talking conductor of said cord circuit in series responsive to the connection of the cord circuit to the trunk, and means responsive to the application of ringing current to said trunk -before said cord circuit 'is connected to said trunk for operating said call signal, and responsive to the application of ringing current to said trunk atter sa'id cord circuit is connected to said trunk for energizing said sleeve relay independent of one of its windings to in,- crease the current flow in said non-talking conductor to cause the operation oztsaid cord sign- In atelephone system, a trunkcompria V talking conductors and a sleeve conducto ,a cord circuit, a (double-wound sleeve relay for the trunk, a signal in said cord cjircur, eans for Operating said elay e a circuit inc'ludi both its windings, said sleeve .ca li i l .etcw "and sai in seri s responsi've to the connectlono-f said cord circuit to said trunk, and means responsive to the application of ringing current to the talking conductors of said trunk for shunting one winding of said relay to increase the flow of current in the sleeve conductor of said trunk to cause the operation of said signal.

Ina-telephone system, a trunk line having-talking conductors and a sleeve -conductor, a call signal for said trunk line, a cord circuit and means for connecting it to said trunk line, a disconnect signal connected to the sleeve of said cord circuit, a control conductor normally connected to said call signal, 4

means respo'nsiveto the application of signalling current to said trunk line for applying a potential to said control conductor to operate said call signal, and means responsive to the connection of said cord circuit to said 1 trunk line for connecting said control conductor to said sleeve conductor so that a subsequent application ot a potential to said control conductor will operate said disconnect signal.

4. In a telephone system, a trunk line, a

said -relay,a cord circuit, a double-wound unlocking relay, means responsive to the co nection of said cord circuitto said trunk line for momentarily closing a circuit including one winding of said unlocking relay to cause it to operate "and unlock saidsignal control relay, and means eliective when said cord circuit is disconnected from said 'truulr line for 'lmo-mentarily closing a circuit including the other winding oi said unlocking relay to causeit to operate and unlocksa'id signalcontrol relay in case it is operated afterthe cord circuit is connected to the trunk line.

6. In a telephone system, a trunk line, a self-locking signal-control relay, means controlled over saidtrunk line for operating said relay, a cord circuit, an unlocking relay, means for momentarily operating said unlocking relay responsive to the-connection of said cord circuit to' said trunk "line to unlock suit is connected tot-he trunk line, and means .v

while the cord circuit is connected to the trunk line.

7. In a telephone system, a trunk line, a self-locking signal-control relay, means controlled over the trunk line for operating said relay, a cord circuit, a double-wound unlocking relay, means for momentarily closing a circuit including one winding of said unlocking relay responsive to the connection of said cord circuit to said trunk line to cause it to operate and unlock said signal-control relay, a key in said cord circuit for causing a reoperation of said last means to unlock said signal-control means in case it is operated while said cord circuit is connected to said trunk line, and means effective when said cord circuit is disconnected from said trunk line for momentarily closing a circuit'including the other winding of said unlocking relay to cause it to operate and unlock-said signal-control relay in case it is operated while said cord circuit is connected to said trunk line.

8. In a telephone system, a trunk line, a cord circuit, a double-wound relay for the trunk, means for establishing an operating circuit for said relay including its two windings in series when said cord circuit is connected to said trunk line, means controlled at will over said trunk line for shunting one winding of said relay, means in said cord circuit for limiting the current flow in said circuit sufiiciently to cause said relay to restore providing one winding ofsaid relay is shunted, and other means in said cord circuit for limiting the current flow in said circuit sufficiently to cause said relay to restore when energized over its two windings in series.

9. In a telephone system, a trunk, a cord circuit and means for connecting it to said trunk, a sleeve relay for the trunk responsive to the connection of said cord circuit to said trunk, a signalling relay for applying signalling current to said trunk, a key in said cord circuit,'contacts on said key for causing the release of said sleeve relay when the key is operated, means responsive to the release of said sleeve relay for connecting said signalling relay to one talking conductor of said trunk, and contacts on said key for closing an energizing circuit including said one talking conductor for said signalling relay when the keyis operated.

10. In a telephone system, a trunk line, comprising talking conductors and a sleeve conductor, means for extending a connection to said trunk, a sleeve relay connected to said sleeve conductor, means responsive to the extension of a connection to said trunk for establishing a flow of current in said sleeve conductor to operate said relay. a signalling relay for applying signalling current to said talking conductor, means for decreasing the flow of current in said sleeve conductor to restore said sleeve relay, means responsive to the restoration of said sleeve relay for con necting said signalling relay to one of said talking conductors, and means for thencausing the operation of said signalling relay.

11. In a telephone system, a trunk line terminating in two jacks, a signal for each jack, a transfer relay, a sleeve relay connected to the first jack through contacts on said transfer relay and connectedto the second jack directly, means for operating the signal of the first jack when acall is extended over said trunk line, means for operating said sleeve relay when the call is answered via the first jack to restore the signal thereof, a key for operating the signal of said second jack and for operating said transferrelay to cause said sleeve relay to restore, a locking circuit for said transfer relay, and means controlled by said sleeve relay for opening said locking circuit to cause said transfer relay to restore responsive to the answering of the call via said second jack.

12. In a telephone system, a trunk com prising talking conductors and a sleeve con: ductor, a cord circuit adapted to be connected to said trunk, a key for said cord circuit, a relay for connecting ringing current to said trunk, and circuit connections including one talking conductor and the sleeve conductor of the trunk and said key for operating said relay.

13. In a trunk terminating in two acks, asignal for each jack, a key for the first jack, a sleeve relay normally connected to both jacks, means for operating the signal at the first jack responsive to the extension of a call over the trunk, and means for operating the signal at the second jack and for disconnecting the sleeve relay from the first jack responsive to the operation of said key.

14. In a trunk terminating in two jacks with individual signals for the jacks, a key for the first jack,a sleeve relay normally connected to both jacks, means for actuating the signal at the first jack responsive to the extension of a call over the trunk, means for actuating the signal at the second jack and for disconnecting the sleeve relay from the first ack responsive to the operation of said key, and means for deactuating both said signals responsive to the answering of the call from the second jack.

15. In a trunk circuit terminating in an answering jack, a signal control relay operated responsive to a call over the trunk, an unlocking relay for controlling said signal relay, a third relay, a key, contacts on the jack for operating said unlocking relay responsive to the answering of a call, and contacts on said third relay for operating said unlocking relay responsive to the actuation with the jack, a sleeve relay for-the trunk,

of said key.

16. A trunk terminating in a jack, a visual signal, two relays, circuit connections including contacts on the jack for operating the first of said relays eflective when the second relay is normal, and circuit connections for operating the first of said relays in series with said signal eflective when the second relay is actuated.

17. In a telephone system,'a trunk terminating in a jack, a cord circuitincluding a plug adapted to co-operate with the jack, a relay for the trunk said relay having two windings, means for momentarily operating the relay over a circuit including one winding responsive to the insertion or" the plug in the jack, and means for momentarily reoperating said relay over a circuit including the other Winding responsive to the withdrawal of the plug from the jack.

18. In a telephone system, a trunk terminating in a jack, a cord circuit including a plug adapted to co-operate with the jack, a relay and a visual busy signal for the trunk, means for momentarily operating the relay over a circuit including contacts on the jack responsive to the insertion of the plug in the ack, and means for momentarily reoperating said relay in series with said signal responsive to the withdrawal of the plug from the ack.

19. In a telephone system, a trunk circuit including a sleeve relay, two windings for the relay, said windings being connected in series to a source of current through a resistance, means responsive to the answering of a call over the trunk for momentarily shunting said resistance and for operating said relay over the two windings in series, and means subsequently controlled over the trunk for shunting said resistance and one of said windings and for maintaining said relay operated over the other winding.

20. I11 a telephone system, a trunk and means for extending a call thereover, means for answering the call, a sleeve relay for the trunk normally connected to ground through a resistance, and means responsive to the an swering of the call for momentarily short circuiting said resistance to complete an operating circuit for said relay.

21. In a telephone system, a trunk, means for extending a call over the trunk, means for answering the call, a battery, a relay in said trunk, a sleeve conductor for the trunk extending through the winding of said relay and a resistance in series therewith to one pole of said battery, and means responsive to the answering ota call for connecting the other pole of said battery to said sleeve conductor and for momentarily short-circuiting said resistance to operate said relay.

22. In a telephone system, a trunk terminating in a jack, a plug adapted to co-operate an operating circuit for said relay closednio-z mentarily responsive, tov the insertion ot; the p ug in th 1' b at imm ng eireliit ior a -r y cl din fn rm sq ineet o to a source ofcurren-t through a resistance,

2 Iii a e ep en sy em, a trun .liee i1 cluding a sleeveconductonarelay connected 9 s dendu r, a ner wrs. li k, as nal for said linik, means responsivegto the connection 0t thelink to the trunk line for connecting said signal and said relay via sai-d sleeve conductor to operate the relayjmeans for" limiting the current flowjoverj said sleeve conductorco-prevent the operation of said signal, a relay normally connected to the talking conductors of the trunk line adapted to be disconnected therefrom when ringing current is applied to the near end of the trunk line and to operate responsive to the application of ringing current to the distant end of the trunk line, and means controlled by said second relay for increasing the current flow over said sleeve conductor to operate said signal;

24. In a telephone system, a trunk line terminating in amanual jack, a relay connected to the sleeve of said jack, a cord circuit including a plug adapted to cooperate with said jack, a signal connected to the sleeve of said plug, means responsive to the connection of the cord to the trunk line for establishing a current flow over said sleeves to operate only said relay, a relay normally connected to the trunk line adapted to be disconnected therefrom when ringing current is applied to the near end of the trunk line and to operate when ringing currentis applied to the distant end of the trunk line, and means controlled by said relay for increasing the current flow over said sleeves to operate said signal.

25. In a telephone system, a trunk line com prising talking conductors terminating in a manual jack, a relay connected to the sleeve of said jack, a cord circuit including a plug adapted to cooperate with said jack, means responsive to the connection of the cord with the trunk line for establishing a flow or current over the sleeves of the plug and ack to operate said relay, a source of signalling current, means in the cord circuit for decreasing the flow of current over said sleeve to release said relay, and means effective on the release of said relay for disconnecting the talking conductors from said jack and for connecting them to said current source.

26. In a telephone system a trunk line comprising two talking conductors and a nontalking conductor an operators link circuit and means for connecting it to said trunk line, a source of signallingcurrent, a relay for connecting said two talking conductors to said current source, and means controlled from said link circuit over one of said talkingconductors and said sleeve conductor for operating said relay.

27. In a telephone system, a trunk line comprising two talking conductors, an open ators link circuit and means for connecting it to said trunk line, a source of signalling current, a relay for connecting said talking conductors to said current source, means con trolled from said link circuit for connecting 'said relay to one of said talking conductors at will, and means controlled over said one talking conductor for operating said relay.

'In Witness whereof, I hereunto subscribe my name this 25th day of April, A. D. 1928'.

THOMAS F. CROCKER. 

